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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="coroutine.stack"></a><a class="link" href="stack.html" title="Stack allocation">Stack allocation</a>
</h2></div></div></div>
<div class="toc"><dl class="toc">
<dt><span class="section"><a href="stack/protected_stack_allocator.html">Class <span class="emphasis"><em>protected_stack_allocator</em></span></a></span></dt>
<dt><span class="section"><a href="stack/standard_stack_allocator.html">Class <span class="emphasis"><em>standard_stack_allocator</em></span></a></span></dt>
<dt><span class="section"><a href="stack/segmented_stack_allocator.html">Class <span class="emphasis"><em>segmented_stack_allocator</em></span></a></span></dt>
<dt><span class="section"><a href="stack/stack_traits.html">Class <span class="emphasis"><em>stack_traits</em></span></a></span></dt>
<dt><span class="section"><a href="stack/stack_context.html">Class <span class="emphasis"><em>stack_context</em></span></a></span></dt>
<dt><span class="section"><a href="stack/valgrind.html">Support for valgrind</a></span></dt>
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<p>
      A <span class="emphasis"><em>coroutine</em></span> uses internally a <span class="emphasis"><em>context</em></span>
      which manages a set of registers and a stack. The memory used by the stack
      is allocated/deallocated via a <span class="emphasis"><em>stack-allocator</em></span> which is
      required to model a <span class="emphasis"><em>stack-allocator concept</em></span>.
    </p>
<h4>
<a name="coroutine.stack.h0"></a>
      <span class="phrase"><a name="coroutine.stack._emphasis_stack_allocator_concept__emphasis_"></a></span><a class="link" href="stack.html#coroutine.stack._emphasis_stack_allocator_concept__emphasis_"><span class="emphasis"><em>stack-allocator
      concept</em></span></a>
    </h4>
<p>
      A <span class="emphasis"><em>stack-allocator</em></span> must satisfy the <span class="emphasis"><em>stack-allocator
      concept</em></span> requirements shown in the following table, in which <code class="computeroutput"><span class="identifier">a</span></code> is an object of a <span class="emphasis"><em>stack-allocator</em></span>
      type, <code class="computeroutput"><span class="identifier">sctx</span></code> is a <code class="computeroutput"><span class="identifier">stack_context</span></code>, and <code class="computeroutput"><span class="identifier">size</span></code>
      is a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span></code>:
    </p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
              <p>
                expression
              </p>
            </th>
<th>
              <p>
                return type
              </p>
            </th>
<th>
              <p>
                notes
              </p>
            </th>
</tr></thead>
<tbody>
<tr>
<td>
              <p>
                <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">allocate</span><span class="special">(</span>
                <span class="identifier">sctx</span><span class="special">,</span>
                <span class="identifier">size</span><span class="special">)</span></code>
              </p>
            </td>
<td>
              <p>
                <code class="computeroutput"><span class="keyword">void</span></code>
              </p>
            </td>
<td>
              <p>
                creates a stack of at least <code class="computeroutput"><span class="identifier">size</span></code>
                bytes and stores its pointer and length in <code class="computeroutput"><span class="identifier">sctx</span></code>
              </p>
            </td>
</tr>
<tr>
<td>
              <p>
                <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">deallocate</span><span class="special">(</span>
                <span class="identifier">sctx</span><span class="special">)</span></code>
              </p>
            </td>
<td>
              <p>
                <code class="computeroutput"><span class="keyword">void</span></code>
              </p>
            </td>
<td>
              <p>
                deallocates the stack created by <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">allocate</span><span class="special">()</span></code>
              </p>
            </td>
</tr>
</tbody>
</table></div>
<div class="important"><table border="0" summary="Important">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../doc/src/images/important.png"></td>
<th align="left">Important</th>
</tr>
<tr><td align="left" valign="top"><p>
        The implementation of <code class="computeroutput"><span class="identifier">allocate</span><span class="special">()</span></code> might include logic to protect against
        exceeding the context's available stack size rather than leaving it as undefined
        behaviour.
      </p></td></tr>
</table></div>
<div class="important"><table border="0" summary="Important">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../doc/src/images/important.png"></td>
<th align="left">Important</th>
</tr>
<tr><td align="left" valign="top"><p>
        Calling <code class="computeroutput"><span class="identifier">deallocate</span><span class="special">()</span></code>
        with a <code class="computeroutput"><span class="identifier">stack_context</span></code> not
        set by <code class="computeroutput"><span class="identifier">allocate</span><span class="special">()</span></code>
        results in undefined behaviour.
      </p></td></tr>
</table></div>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
        The stack is not required to be aligned; alignment takes place inside <span class="emphasis"><em>coroutine</em></span>.
      </p></td></tr>
</table></div>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
        Depending on the architecture <code class="computeroutput"><span class="identifier">allocate</span><span class="special">()</span></code> stores an address from the top of the stack
        (growing downwards) or the bottom of the stack (growing upwards).
      </p></td></tr>
</table></div>
<p>
      class <span class="emphasis"><em>stack_allocator</em></span> is a typedef of <span class="emphasis"><em>standard_stack_allocator</em></span>.
    </p>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2009 Oliver Kowalke<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
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